Semiconductor mid-infrared (mid-IR) lasers with a wide tuning range are desirable for many applications such as spectroscopy and biochemical analysis. Tunable quantum cascade (QC) lasers have been demonstrated in several approaches, including single-mode distributed feedback (DFB) lasers, multi-section lasers, heterogeneous active regions, and external cavities (ECs). Each approach has shortcomings. For example, DFB lasers can produce single-mode emission, but have a very limited current-controlled tuning range of approximately 10 inverse centimeters (cm−1). Multi-section lasers, such as two-section lasers with parallel and independent current injection for each section through multiple contacts, can have a large tuning range, but have higher threshold currents and require extra device fabrication steps. EC lasers lack long-term mechanical and vibrational stability and require well-aligned external optics components. A semiconductor laser tunable over a wide range in the mid-IR wavelengths, which provides easier fabrication and simpler components, is desirable.